Air conditioning system expansion valve

ABSTRACT

The invention relates to an expansion valve, designed especially for an air conditioning system in a motor vehicle, that comprises a valve housing with a first high-pressure side port, a second low-pressure side port, and a channel disposed therebetween through which refrigerant can flow. The valve includes a sliding element that is arranged in the channel and can move along a longitudinal axis, wherein an aperture restricts the flow of refrigerant through the channel, and the size and shape of the aperture is defined by the size and shape of the sliding element and the position of the sliding element in the channel. The expansion valve is easy to manufacture and can be universally used based in part on the sliding element extending completely through the channel.

FIELD OF THE INVENTION

The invention generally relates to an expansion valve that may be usedin an air conditioning system, including an automobile air conditioningsystem, and methods of use therefor.

BACKGROUND OF THE INVENTION

Modern air conditioning systems often use a controllable expansion valveto regulate the mass flow rate of an expanding refrigerant. This type ofexpansion valve typically can be set to two positions, i.e., to a closedor open state, depending on an operating parameter of the airconditioning system. The proper operation of the valve helps to insurethat the refrigerant super heats before entering the compressor so thatthe efficiency of the air conditioning system is maintained within anoptimal range. A properly operating expansion valve may reduce the needfor a low-pressure collector to protect the compressor from fluidrefrigerant entering the compressor.

EP 1 001 229 A2 (see also U.S. Pat. No. 6,430,950) describes anexpansion valve for an air conditioning system of a motor vehicle inwhich a sliding needle plunges essentially vertically into an expansionchannel, which channel separates the high-pressure side from thelow-pressure side of the refrigerant cycle. The cross-section of thechannel is partially free, because the sliding needle only partiallyplunges into the channel. When the needle completely penetrates thechannel, the valve is closed. The valve is opened at a maximum when thesliding needle does not extend into the channel at all.

Prior art expansion valves, however, are difficult to manufacture and/orare limited in applicability. In addition, the desirable operating rangeof prior art expansion valves can be difficult to set.

SUMMARY OF THE INVENTION

The invention provides an improved expansion valve for use in arefrigeration circuit that is easy to manufacture and can be in a widevariety of applications.

In preferred embodiment of the invention, a sliding element is fullyinserted in a channel at any state of the expansion valve, and the massflow rate through the valve is dependent on the shape of the slidingelement. Due to the resulting flow along the shape of the slidingelement, the desirable flow characteristics of the refrigerant in thechannel aperture are improved, which correspondingly reduces the noiselevel caused by the valve.

An advantage of a valve made according to the invention is that thesliding element, which may include a control section, is locatedproperly and accurately in every position. In addition, the shaping ofthe control section allows accurate set up of the valve aperture independence on the position of the sliding element. The sliding elementmay be shaped as an elongated body with a constant cross-section at oneend and an adjacent control section that, compared to the end section,has a tapered cross-section. The sliding element and an associatedcontrol section further may be advantageously placed in a slot (or in azone near the slot) in the channel that permits the passage ofrefrigerant from an area of relatively higher pressure to an area ofrelatively lower pressure. The tapering of the control section of thesliding element may be of a constant diameter so that the change of theaperture in dependence on the motion of the sliding element is constant.However, depending on the technical requirements of each system, thetapering may also have a variable cross-section so that theaforementioned dependence is not constant. This design allows for aprecise optimization of the function of the expansion valve according tothe invention, which can improve the efficiency and the reliability ofan air conditioning system. In addition, it is possible, as regards theusability of the expansion valve in air conditioning systems of varioustypes and sizes, to provide a channel and slot for a sliding element ofa sufficiently large diameter, and further to adjust or adapt thedimensions of the tapering in the zone of the control section to aparticular type of air conditioning system.

In order to achieve an acceptable seal between the channel and slidingelement, the diameter of the sliding element at the end can be largerthan the width of flanges that define a sealable opening into thechannel. This design enlarges the sealing surface between the channelwall and the sliding element in various states of the sliding element.It also will be appreciated by persons of skill in the art that thediameter of the channel may be larger, smaller or the same size as thediameter of the sliding element or the aperture into which the slidingelement is placed.

Furthermore, the sliding element may be advantageously shifted by meansof a control mechanism in the direction of the axis, whereby the valveis made settable. In an especially advantageous design, the controlmechanism includes a spring to bias the position of the sliding element.This spring force defines in a simple fashion, a mechanical conditionfor the opening of the valve. In order to ensure that the constructionof the expansion valve is simple and cost-effective, the spring and thecontrol mechanism may be arranged on the same side as the slidingelement.

A control mechanism associated with the valve may further include apressurized membrane. The membrane, which is mechanically connected tothe sliding element, allows for a simple motion of the sliding elementin dependence on the operating parameters of the air conditioningsystem.

In a preferred embodiment, there is a third low-pressure connection forthe refrigerant to the valve housing. A membrane of the controlmechanism may be exposed to the pressure or temperature of therefrigerant, and particularly to the pressure or temperature in thesuction line before the compressor. This design makes it possible tocontrol, in a simple fashion, the sliding element in dependence on aparameter of the refrigerant's state after its expansion.

In a further preferred embodiment, there is a fourth low-pressureconnection for the refrigerant to the valve housing. Refrigerant flowsthrough the third connection into the valve, without any substantialloss of pressure, and then flows out of the valve through the fourthconnection so that the valve housing also forms a part of a low-pressureline of the refrigerant cycle. An expansion valve made according to theinvention may be used in a closed volume system, wherein pressure in thesystem exerts pressure upon the membrane, and wherein the volume is inthermal contact with the third connection. In this manner, thetemperature of the refrigerant, which is adjacent to the thirdconnection, can be directly converted, in a mechanical electromechanicalfashion, into a corresponding activation/triggering of the slidingelement. This conversion occurs in an especially efficient manner if thevolume is filled with a defined quantity of a suitable substance, of,for example, the refrigerant of the air conditioning system.

As an alternative to exerting pressure upon the membrane from a closedvolume, the membrane can also be exposed to a force exerted by the airconditioning system's refrigerant's pressure, and particularly to arefrigerant under high pressure. Such a design of the control mechanismcan be particularly advantageous in the case of CO₂ air conditioningsystems, which—compared to conventional air conditioning systems—havesomewhat significantly different operation parameters.

In the interest of a simple construction and reduction of the number ofcomponents, the sliding element may be set to a default setting bypositioning the control mechanism in a particular relation to the valvehousing. In this arrangement there is no need for any additionaladjustment of screws, and only the attachment and sealing of the controlmechanism in relation to the valve housing requires special designattention.

Further advantages and features of the expansion valve as designed bythis invention become apparent from the subsequent design example andfrom the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a cross-section of an expansion valve of theinvention.

FIG. 2 is an exploded view of region A of FIG. 1.

FIG. 3 is a top view of a cross-section through the expansion valve fromFIG. 1 along the line B-B in the closed state of the valve.

FIG. 4 is a top view of a cross-section through the expansion valve fromFIG. 1 along the line B-B in an at least partially open state of thevalve.

FIG. 5 is a top view of an alternative embodiment of the cross-sectionthrough the expansion valve from FIG. 1 along the line B-B in the closedstate of the valve.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an expansion valve in accordance with the invention.This valve includes a valve housing 1, which may consist of severalcomponents in order to simplify its assembly.

A zone of the valve housing, shown at the lower section of the housing 1in FIG. 1, includes a first port 2 and a second port 3, which in apreferred embodiment may be located at the same height and preferably inthe same axis. The first port 2 is connected with a refrigerant linethat comes from the condenser of the refrigeration circuit, and, ingeneral, is part of the high-pressure section of the refrigerationcircuit. The second port 3 is part of the low-pressure section of therefrigeration circuit, which, in FIG. 1, is also illustrated by means ofa larger diameter.

In a preferred embodiment, ports 2 and 3 are connected through anexpansion element of the air conditioning system in which previouslycompressed refrigerant expands and cools. The expansion element includesa channel 4, which connects ports 2 and 3, wherein the common axis ofports 2 and 3 is also the middle axis of channel 4.

As illustrated in FIG. 1, channel 4 is intersected by a hole 5 that isvertical to the axis of the channel, and in which is disposed a slidingelement 6. Sliding element 6 is shaped as an elongated body and maytravel along an axis within hole 5. The hole 5 extends on both sides ofthe channel 4, and a downward-leading part of the hole is designed as ablind hole 5 a in the valve housing 1. Channel 4 may have a constant orvarying diameter. In addition, the diameter of channel 4 at theintersection of hole 5 may be larger, smaller or the same size as hole5.

As illustrated in FIG. 2, the sliding element 6 comprises a lower endsection 6 a, which is formed as a dimensionally accurate cylinder. In apreferred embodiment of the invention, the end section 6 a is coupled toa rotationally symmetrical control section 6 b of the sliding element 6that is concentric to the end section 6 a. The diameter of the controlsection 6 b is conically tapered and has a cross-section that is smallerthan the cross-section of the end section 6 a. Overall, the controlsection forms a rotationally symmetrical truncated cone. The controlsection 6 b may have other shapes and forms, and can also be shaped, forexample, as a cylindrical body with an aperture.

The control section 6 b is coupled to a cylindrical shaft 6 c of thesliding element 6, which, in the example of FIG. 2, has the samediameter as the lower end section. It is noted, however, that thediameters of these shafts may differ depending on the desiredcharacteristics.

FIGS. 3 and 4 illustrate the sliding element 6 in different operatingpositions. As is apparent from these figures, the movement of thesliding element along its longitudinal axis sets up a variable aperture14 of the channel 4.

As illustrated in FIG. 3, in the uppermost shifted position of thesliding element, the end section 6 a is completely inserted into channel4. As one of ordinary skill in the art will appreciate, the dimensionsof the components are selected (for example, by finely grinding the hole5 and the end section 6 a) such that a sealing closure, at least in thesense of the function of the air conditioning system is established. Acomplete hermetic sealing in the strict sense of the term is usually notrequired, however. In order to achieve an appropriate seal, the diameterof the end section 6 a may be noticeably larger than the diameter of thechannel 4, which creates a particularly large contact surface. An endsection 6 a is arranged only between two flanges 4 a located in thechannel 4, which also achieves a sufficient seal. In the design of apreferred embodiment, the flanges 4 a or another insert formeddifferently but having the same function in the channel 4 can be made ofa material with the same properties of thermal expansion as the slidingelement 6.

FIG. 5 illustrates an alternative structure of lower end section 6 a. Inthis embodiment, a portion of lower end section 6 a has been machined toa flat shape, as indicated by reference number 6 d. This structurepermits displacement of any fluid or material captured in blind hole 5 aas sliding element moves into blind hole 5 a. In an embodiment of theinvention, the width of the non-circular feature 6 d is less than thewidth of the flanges 4 a in order to reduce the possibility of leakage,as the rotational orientation of the sliding element 6 with respect tochannel 4 may change over time.

If, starting from its closed position (see FIG. 3), the sliding element6 is moved downward as shown in FIG. 1, the control section 6 b crossesthe channel 4. The end section 6 a plunges into the blind-hole zone 5 aof the hole 5. In this arrangement, the channel 4 is completelypenetrated by the sliding element 6 regardless of the operatingconditions of the expansion valve. The tapering of the control sectioncreates an aperture 14, which varies depending on the position of thesliding element. In the area of the aperture, the refrigerant expands ina controlled fashion and flows along the outer circumference of thecontrol section 6 b of the sliding element 6 in a plane that isessentially vertical to the longitudinal axis of the sliding element 6.In FIG. 4, the flowing of the refrigerant is indicated by means ofarrows. Overall, this process results in the low-noise expansion of therefrigerant.

Due to the conical tapering of the control section 6 b, the aperture 14is not enlarged in a linear relation to the longitudinal motion of thesliding element 6, but—as, for example, in a preferred embodiment asillustrated in FIGS. 1-4—in an essentially quadratic relation. Thus, themass flow of refrigerant does not always depend on an operationparameter in a linear manner. In general, a suitable shaping of thecontrol section 6 allows for the accurate adjustment of an expansionvalve to a control parameter.

The shaft 6 c of the sliding element passes through various portions ofvalve housing 1. A sealing element 7 seals shaft 6 c at the point ofpenetration of control channel 8. An o-ring completely surrounds andseals the shaft 6 from control channel 8. In this manner, the contactsurface between the shaft 6 c and the wall of hole 5 can bepressure-sealed from control channel 8.

Control channel 8 extends through valve housing 1 and is separate fromchannel 4 in a preferred embodiment. It is also possible, however, thatchannel 8 may be more directly coupled to channel 4. In the embodimentillustrated in FIG. 1, channel 8 includes a third port 8 a and a fourthport 8 b. The third port 8 a is connected to an outlet of an evaporatorof the refrigerant circuit, and the fourth port 8 b is connected to thesuction inlet of a compressor of the refrigerant circuit. Thus, inrelation to the circuit, the refrigerant—when flowing through thecontrol channel 8—is in its lowest pressure zone, which is alsoreflected in the larger diameter of ports 8 a and 8 b as compared tothose of ports 2 and 3.

Shaft 6 c crosses the control channel 8 and terminates in a plunger 6 dof the sliding element 6. Plunger 6 d passes through a hole in thehousing area 1 a. An upper end surface of the plunger 6 d is, at leastin one direction, in a non-positive connection with the membrane 9. Themembrane 9 is held in a housing 10, wherein an upper part of membranehousing 10 and the side of the membrane opposite the membrane'sconnection with the plunger 9 hermetically close off a volume 11. Insidemembrane housing 10 is a sealing plug 12, by means of which the volume11 can be filled with a defined quantity of a substance under certaindefined conditions, e.g., pressure or temperature. A collar 10 a of themembrane housing is held, by means of a thread, in the hole through thevalve housing 1 a, and sealing means (not shown) ensure that the controlchannel 8 is sealed. The plunger 6 d longitudinally slides along aninternal side of the collar 10 a.

The plunger assembly may be screwed into place, within a tolerancerange, of different depths and in a sealing connection, which allows thedepth at which the sliding element 6 plunges into the hole to bepre-set. This arrangement compensates for the tolerances in themanufacture of individual components.

Sliding element 6 is also supported against the lower side of thecontrol channel 8 by means of a helical spring 13, wherein the helicalspring 13 envelops the shaft 6 c and rests against the plunger 6 d. Thesliding element is thus biased in a direction of the spring force.

Spring 13, membrane 9, membrane housing 10, and enclosed volume 11 forma control mechanism, by means of which the sliding element 6 is moved,in a controlled manner, in dependence on the operation parameters of theair conditioning system. In this configuration, three forces act uponthe sliding element, i.e., the pressure force of the refrigerant in thecontrol channel 8, the spring force of spring 13, and the pressure forceexerted by the volume 11. The substance contained in volume 11 exerts aforce on membrane 9 and acts in a direction opposite to the two otherforces. Thus, in the direction of its longitudinal axis, the position ofsliding element will be determined by the interaction of these forces.The pressure force of the refrigerant in channel 4 acting on the slidingelement is limited because at that location, the sliding element 6 has arelatively small cross-section.

Through the surface of membrane 9 and the interstice between the plunger6 d and the collar 10 a, volume 11 is in thermal contact with therefrigerant of the control channel 8. A decrease in the pressure of therefrigerant in control channel 8 (typically, after an evaporator) and anincrease in the temperature of the refrigerant in the control channel 8result in a net increase of the force component acting against theopposing forces in a direction of the spring force. The sliding element6, therefore, moves downward in the opening direction. In contrast, adecrease in the temperature in the zone of the control channel 8 resultsin the aperture 14 being closed. A reduced mass flow of the refrigerantin the evaporator then causes an increase in the temperature of therefrigerant in the control channel 8 and/or in the suction line of thecompressor. In this manner, a mechanical control circuit arises,which—after a proper pre-alignment and setting of the controlmechanism—ensures that the refrigerant sufficiently superheats after theevaporator. This results in a good efficiency of the air conditioningsystem and reduces the possibility that condensed refrigerant will enterthe compressor.

It is a matter of course that the properties of the expansion valve asdesigned by this invention are not restricted to the embodiments asillustrated and described above. The control of the sliding element canbe realized in any known form including a purely electromechanicalcontrol in conjunction with an electronic control device.

While the invention has been described with an emphasis upon particularembodiments, it should be understood that the foregoing description hasbeen limited to the presently contemplated best mode for practicing theinvention. It will be apparent that various modifications may be made tothe invention, and that some or all of the advantages of the inventionmay be obtained. Also, the invention is not intended to require each ofthe above-described features and aspects or combinations thereof. Inmany instances, certain features and aspects are not essential forpracticing other features and aspects. The invention should only belimited by the appended claims and equivalents thereof, since the claimsare intended to cover other variations and modifications even though notwithin their literal scope.

1. An expansion valve, especially for an air conditioning system of amotor vehicle, comprising: a valve housing that includes a first portand a second port and a first refrigerant channel disposed between thefirst and second ports; and a sliding valve element that is capable ofmovement that defines a stroke along a longitudinal axis, wherein theposition of the valve element along its stroke determines the amount ofrefrigerant that may flow in the channel and wherein the sliding elementcompletely extends through the channel throughout its stroke.
 2. Anexpansion valve according to claim 1, wherein the valve element isdisposed in a hole that crosses the refrigerant channel.
 3. An expansionvalve according to claim 1, wherein the valve element comprises anelongated body that includes an end section of a constant cross-sectionand a directly adjacent control section with a tapered cross-section. 4.An expansion valve according to claim 3, wherein the control section ofthe valve element includes a cross-section that changes over its length.5. An expansion valve according to claims 3, wherein the diameter of endsection of the valve element is larger than the diameter of the firstrefrigerant channel.
 6. An expansion valve according to claim 1, whereina control mechanism determines the position of the valve element in itsstroke.
 7. An expansion valve according to claim 6, wherein the controlmechanism includes a spring that exerts a force upon the valve element.8. An expansion valve according to claim 7, wherein the spring and thecontrol mechanism are disposed on the same side of the first refrigerantchannel.
 9. An expansion valve according to claims 6, wherein thecontrol mechanism includes a pressure-loaded membrane.
 10. An expansionvalve according to claim 9, wherein the valve housing further includes athird port.
 11. An expansion valve according to claim 10, wherein thevalve housing further includes a fourth port and a second refrigerantchannel disposed between the third and fourth ports.
 12. An expansionvalve according to claim 10, wherein the pressure of refrigerantavailable at the third port exerts a force upon the membrane.
 13. Anexpansion valve according to claim 10, wherein a closed volume exertspressure upon the membrane and wherein the volume is in thermal contactwith refrigerant available at the third port.
 14. An expansion valveaccording to claim 10, wherein the pressure of refrigerant in arefrigerant channel exerts a force upon the membrane.
 15. An expansionvalve according to claim 10, wherein the initial position of the valveelement is determined by position of the control mechanism in relationto the valve housing.